tools(deps-dev): Update symfony/config requirement in /tools/phpmd

Updates the requirements on [symfony/config](https://github.com/symfony/config) to permit the latest version.
- [Release notes](https://github.com/symfony/config/releases)
- [Changelog](https://github.com/symfony/config/blob/7.1/CHANGELOG.md)
- [Commits](symfony/config@v2.0.0...v7.1.1)

---
updated-dependencies:
- dependency-name: symfony/config
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

tools/phpmd/composer.json

@@ -7,7 +7,7 @@
     },
     "require-dev": {
         "phpmd/phpmd": "2.15.0",
-        "symfony/config": "<7",
+        "symfony/config": "<8",
         "roave/security-advisories": "dev-latest"
     },
     "prefer-stable": true,